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association#build inconsistency

#990

When building an object through an association, the resulting object isn't bound to the proxy owner if the proxy owner is a new record. If the proxy owner is already saved, it is bound.

I think this is inconsistent.

This also boils down to using find_or_initialize_by or find_or_create_by on associations on new records.


class User < ActiveRecord::Base
  has_many :posts, :dependent => :destroy
end

class Post < ActiveRecord::Base
  belongs_to :user
end

>> u=User.first
=> #<User id: 1, name: "user 1", created_at: "2008-09-07 22:07:35", updated_at: "2008-09-07 22:07:35">
>> u2=User.new
=> #<User id: nil, name: nil, created_at: nil, updated_at: nil>

>> u.posts.build.user
=> #<User id: 1, name: "user 1", created_at: "2008-09-07 22:07:35", updated_at: "2008-09-07 22:07:35">
>> u2.posts.build.user
=> nil

>> u.posts.find_or_initialize_by_title('title').user
=> #<User id: 1, name: "user 1", created_at: "2008-09-07 22:07:35", updated_at: "2008-09-07 22:07:35">
>> u2.posts.find_or_initialize_by_title('title').user
=> nil

Reported by Mathijs Kwik · September 7th, 2008 @ 11:22 PM

Activity

Pratik
- Assigned user set to Michael Koziarski
- State changed from new to wontfix
Please reopen once we have a patch for this.

This looks similar to an ID map patch Koz has been involved with, so assigning the ticket to him.

December 20th, 2008 @ 03:32 PM
Prem Sichanugrist (sikachu)
I just wonder ..

I've looked at the code, and I found out that the association's build method is done by setting foreign_key to be the parent's id. Can we also do something like set the attribute with the name of the parent object to be refer to parent object?

February 1st, 2009 @ 06:24 AM
Ryan Bigg
- State changed from wontfix to open
Marked a similar ticket, #4497 ActiveRecord associations .build does not set associations., as a duplicate of this one and asked the user to submit a patch here.

April 29th, 2010 @ 12:52 AM
Evgeniy Dolzhenko
Btw. shouldn't :inverse_of association options handle this?

April 29th, 2010 @ 07:08 AM
Jeremy Kemper
- Milestone changed from 2.x to 3.x
[bulk edit]

May 4th, 2010 @ 06:48 PM
Andreas Mayer
Have the same problem. Using the workaround. Will this be fixed in Rails 3 final?

July 31st, 2010 @ 12:05 AM

Neeraj Singh

State changed from open to resolved
Importance changed from to Low

As Evgeniy Dolzhenko suggested setting inverse_of resolves the issue.

class Car < ActiveRecord::Base
  has_many :brakes, :inverse_of => :car
end

class Brake < ActiveRecord::Base
  belongs_to :car, :inverse_of => :brakes
end

> Car.first.brakes.build.car
  Car Load (0.4ms)  SELECT "cars".* FROM "cars" LIMIT 1
 => #<Car id: 1, name: nil> 

> Car.new.brakes.build.car
 => #<Car id: nil, name: nil> 

> Car.create.brakes.build.car
  SQL (0.5ms)  INSERT INTO "cars" ("name") VALUES (NULL)
 => #<Car id: 2, name: nil>


> Car.last.brakes.find_or_initialize_by_name('cool').car
  Car Load (0.6ms)  SELECT "cars".* FROM "cars" ORDER BY cars.id DESC LIMIT 1
  Brake Load (0.2ms)  SELECT "brakes".* FROM "brakes" WHERE ("brakes".car_id = 2) AND ("brakes"."name" = 'cool') LIMIT 1
  Car Load (0.1ms)  SELECT "cars".* FROM "cars" WHERE ("cars"."id" = 2) LIMIT 1
 => #<Car id: 2, name: nil> 

> Car.last.brakes.find_or_create_by_name('cool').car
  Car Load (0.4ms)  SELECT "cars".* FROM "cars" ORDER BY cars.id DESC LIMIT 1
  Brake Load (0.3ms)  SELECT "brakes".* FROM "brakes" WHERE ("brakes".car_id = 2) AND ("brakes"."name" = 'cool') LIMIT 1
  SQL (0.3ms)  INSERT INTO "brakes" ("car_id", "name") VALUES (2, 'cool')
 => #<Car id: 2, name: nil>

tested with rails edge.

August 13th, 2010 @ 03:03 PM